The invention relates to a universal tire pressure sensor. In particular, the invention relates to a tire pressure sensor that can be configured to communicate in a simple manner with numerous vehicle-side tire pressure monitoring systems (TPMS).
Automatic tire pressure monitoring systems are known in the prior art. The use of such systems helps drivers thereby to always drive with the correct tire filling pressure, because the driver is informed by a corresponding warning message in the passenger compartment when there is a deviation from the correct pressure. The correct tire pressure has an effect on the safety, optimal driving dynamics, and also on driving comfort.
So-called direct tire pressure monitoring systems function in a particularly precise manner. Tire pressure sensors detect the tire pressure at each tire, and if applicable, other tire data, e.g. temperature. These data are transmitted, together with an identifier of the tire pressure sensor, to a control device in the vehicle, by means of a radio signal. By way of example, a data transmission of this type can occur in the range of 434 MHz or 315 MHz (high frequency communication, or HF-communication).
A communication from the vehicle-side control unit with the tire pressure sensors occurs with so-called triggered systems after transmission of a query signal by means of the control device; this request can be made in the low frequency range (e.g. 125 kHz). Due to the low frequency, the transmission range of a low frequency signal, such as one in the range of 125 kHz, is short. With a suitable dimensioning, a control device-side trigger transmitter can be configured such that the transmission range is only a few meters, such that only the tires on the actual vehicle are addressed. There are systems having numerous trigger transmitters as well as those having a single trigger transmitter.
The tire pressure sensor responds to the trigger, as specified above, in a wireless manner, e.g. with a data protocol in the high frequency range.
Systems that function entirely without triggers, and which transmit data from the tire sensors as a function of condition changes, are also known and typical.
A method and system for a wireless tire pressure monitoring is known, for example, from EP 2 280 837 B1.
Another monitoring method is described in WO 2013/022435.
US 2005/0104722 A1 describes a so-called universal tire pressure sensor in accordance with the preamble of claim 1.
Tire pressure sensors contain some kind of power source or energy storage unit, such as a battery or a Piezo-generator, for example. Moreover, a pressure sensor, and optionally a temperature sensor, are provided, which are coupled to a microcontroller. The typical tire pressure sensors have a high frequency transmitter with an antenna associated therewith, and a low frequency receiver, having a coil associated therewith. It is also possible, however, to implement systems having only high frequency reception/transmission technology. Optionally, acceleration sensors and oscillating crystals are provided in the sensor assembly. Many of the components can be integrated in a standardized integrated circuit, a so-called sensor IC.
Despite the uniformity of the components in a tire pressure sensor, the sensors must be adjusted to the vehicle systems with respect to the transmission of acquired data and other characteristics. By way of example, different vehicle manufacturers have different requirements regarding carrier frequency, modulation of the signal, data formats or encoding technologies for the signals.
Recently, it has been attempted to provide numerous vehicles with standardized sensors. For systems of this type, the term “universal sensor” (universal tire pressure sensor) has been established. As a rule, a distinction is made thereby between programmable universal sensors, multi-protocol universal sensors, and configurable universal sensors.
A programmable universal sensor receives a complete, vehicle-specific programming by means of a comprehensive programming, usually transmitted in a wireless manner, which can require a few tens of seconds to as much as a few minutes. The time required for this programming and the susceptibility to transmission error has rendered a system of this type less acceptable, considering the large number of tires to be mounted in a garage.
The so-called multi-protocol universal sensors, in contrast to programmable universal sensors, are already programed, such that the comprehensive programming procedure is omitted. The specific transmission protocols and the other sensor parameters for different vehicles, however, cannot all be contained in the memory of a tire pressure sensor. As a result, each sensor is applicable for a sub-group of vehicles, wherein the sensor in these various configurations transmits its acquired data in succession. The control device comprehends only a portion of the transmitted data, and the rest is discarded. As a result, only a fraction of the data transmitted by the sensor actually also serves the message transmission, such that a strongly increased power consumption results, and furthermore, disruptions in the communication environment may also be caused due to the messages not being used.
A further development concerns a so-called configurable universal sensor, which is programmed from the start with numerous transmission protocols and parameters, but still requires some critical data before it can establish communication with the vehicle-side device. Thus, an appropriate configuration is selected from a set of stored configurations, according to which the operation can be subsequently executed. After successful configuration, the universal sensor, which has been configured once, subsequently transmits only the appropriate protocol. The data required for the configuration comprise only a small amount of data, the transmitted data quantity is thus less, by orders of magnitude, than with a complete programming. The sensor is only informed as to which of its stored configurations it is to make use of for communication.
All of the systems specified above have disadvantages. On the one hand, with a system for a tire pressure sensor isolated from the rest of the environment, the lowest possible power consumption is a factor, and on the other hand, a quick programming with a comprehensive coverage of vehicles by means of a single sensor model is of significance. Ideally, a truly universal sensor could be created, which also exhibits a low power consumption.